This invention relates to grafted hydrocarbon resins and oligomer compositions, including, but not limited to, adhesives and adhesive components incorporating the grafted compositions, and methods for making and using the compositions.
Relatively low molecular weight resins (usually with molecular weights ranging from 400 to 1500 Mn) are useful in many applications, including tackifying agents for adhesives, ink additives, polymer additives, road marking resins, paper sizing and pipe wrapping. Certain commercial grades of tall oil rosin esters (TOREs) or terpene phenolic resins (TPRs) are used to improve the performance of ethylene vinyl acetate (EVA)-based hot-melt adhesives (HMAs). TOREs, however, suffer from color instability and odor generation at application temperatures. Hydrocarbon resins, particularly hydrogenated cycloaliphatic resins, are superior in color stability and odor generation, but do not exhibit high all-around performance on polar surfaces, such as polyethylene terephthalate (PET) and acrylic varnishes, where TOREs are often used. The adhesive industry recognizes this problem but has yet to achieve a solution. Thus, a need exists for a hydrocarbon resin or an adhesive component having enhanced HMA performance without the instability and odor generation normally associated with TOREs or TPRs.
U.S. Pat. No. 4,719,260 discloses a hot-melt adhesive composition comprising an amorphous polymer containing polypropylene and a graft copolymer of a polycyclic saturated aliphatic hydrocarbon resin and maleic anhydride having improved adhesion to substrates such as polyethylene. It does not disclose the use of an at least partially hydrogenated aromatic hydrocarbon resin. Further, it is generally known that aromatic resins are generally less compatible with saturated hydrocarbon polymers such as those described in U.S. Pat. No. 4,719,260 and do not exhibit the same advantages in adhering to substrates such as polyethylene.
U.S. Pat. No. 3,161,620 discloses a process for reacting maleic anhydride with thermally-produced hydrocarbon resins. It does not disclose at least partially hydrogenating the resin or oligomers before reaction with the maleic anhydride.
EP 0 088 510 discloses polar synthetic petroleum resins. In the embodiments disclosed therein the cyclopentadiene oligomer mixture is reacted with a carboxylic acid or anhydride such as phthalic or maleic acids and then hydrogenated. The reaction proceeds via the acid group reacting with the unsaturation of the resin oligomer thus forming an ester group at the point of attachment. The resulting resin product can be generally classified as a norbornyl ester. The grafted materials disclosed herein are believed to be produced through a different route, namely via an unsaturated bond of the acid or anhydride onto the resin which is preferably at least partially hydrogenated and more preferably substantially hydrogenated as defined herein.
Performance of hydrocarbon resins, particularly hydrogenated aromatic cycloaliphatic resins, on polar surfaces can be improved by modifying the resins to include polar functionality. Grafting functional components onto conventional hydrocarbon resins and/or resin oligomers and optionally combining the grafted resin or grafted oligomer material with another tackifying resin or other adhesive components improves performance and provides advantages over TOREs and TPRs when used in hot melt and other adhesive formulations. In particular, applicants have found that the adhesive materials incorporating these grafted components have improved compatibility with polar polymers such as EVA copolymers and exhibit good performance on difficult substrates, such as coated packaging surfaces.